Castle Unit Reinforcements, when ?

[Mystic Phoenix]

According to the save game scanner there are 18 locations/occasions for spawning new armies. Here they are:

1 Debir Island : Castle of King Frederick - Receive 1st stone and pet dragon
2 Debir Island : Snake-catcher's hut - Kill the snakes in the snakecatcher's hut (quest Snakes on the loose)
3 Debir Island : Castle of King Frederick - receive the 2nd stone
4 Debir Island : Royal University - receive the 2nd stone
5 Debir Island : Castle of King Frederick - receive the 4th stone
6 Debir Island : Royal University - receive the 4th stone
7 Debir Island : Castle of King Frederick - receive the 6th stone
8 Debir Island : Royal University - receive the 6th stone
9 Isle of the Scarlet Wind : Smugglers den - Complete the quest Contraband Searcher
10 Isle of the Scarlet Wind : Great Wave Fortress - Complete the bounty hunt on Richard the Cruel and Recruiter Hector Norbu
11 Bolo Island : Rolf's Drakkar - Complete the quest Run-away Erica by defeating Rolf Wanderer in battle
12 Continent of Verona : House of Champion - Defeat Arnold Henninghem, the Champion
13 Montero Mines : Manufacturing facility - Complete the quest Levers and Gears
14 Continent of Montero : Linkage Factory - Talk to master Neotar about a special weapon after killing the Driller
15 Grand Canal : Lan Mandrake - Complete the Treasures of the Abyss quest
16 Continent of Reha : Sleeping Snake Temple - Accept the contract to kill K'Tahu
17 Sheterra Island : Asklepy's Laboratory - Complete the quest Plight of the Slave, by killing Asklepy
18 Lands of Samman : Castle of Samman - Kill Samman, the Lord of Shettera